This invention relates generally to orthodontic devices and, in particular, to an improved pivot casing for a fixed mandibular arch and maxillary arch expanders which are connected together to allow for forward posturing of the mandible on closure.
Orthodontists treating children often need to gain space in a child's mouth for unerupted mandibular incisors and to increase intercanine distance for narrow archforms, as well as to distilize mandibular first molars so that a total increase of archlength is available in the lower dental arch from first molar to first molar. Furthermore, the orthodontist may want to expand the palate correspondingly.
Mandibular and maxillary arch expanders are known in the art to expand and lengthen the mandibular and maxillary archlengths. The use of such arch expanders help avoid the need for tooth extraction of permanent teeth due to overcrowding. However, such mandibular arch expanders are rather bulky in design, impede tongue mobility, are uncomfortable to wear, and interfere with good oral hygiene. The devices must be substantial in design to resist torquing or leverage mechanics during chewing.
To facilitate corresponding enlargement of the maxillary and mandibular arches, telescoping mechanisms have been employed which encourage forward repositioning of the lower jaw as the patient closes into occlusion. Such devices are commonly referred to as Herbst appliances. Current Herbst appliances include a hollow tube and a rod which is telescopically received in the tube. The tube is connected to the maxillary arch expander and the rod is connected to the mandibular arch expander. Generally, the tube and rod are connected to a band or stainless steel crown by a pivoting connection. The pivot generally comprises a base casing which is soldered or welded to the band or crown and a screw that is inserted through an eye formed on the end of the hollow tube or rod. The screw threadedly engages the base casing and tightened, leaving enough clearance for the eye to pivot about the screw. Often the orthodontist uses an arch wire connected between the two ends of the arch expander. In the past, to accommodate the arch wire, the orthodontist or technician first must attach a rectangular wire tube to the band or crown and then attach the base case on top of the rectangular tube. This arrangement has a relatively high profile caused by the stacking of the rectangular tube and base casing along with the increased solder mass.